This application relates to photographic products and processes for forming a dye image from a colorless precursor of a preformed image dye and to novel compounds which are useful in such products and processes.
U.S. Pat. No. 3,719,489 describes and claims photographic processes employing initially photographically inert compounds which are capable of undergoing cleavage in the presence of the imagewise distribution of silver ions made available during processing of a silver halide emulsion to liberate a reagent, such as, a photographically active reagent or a dye in an imagewise distribution corresponding to that of said silver ions. In one embodiment disclosed therein, color images are produced by using as the photographically inert compounds, color providing compounds which are substantially non-diffusible in the photographic processing composition but capable of undergoing cleavage in the presence of the imagewise distribution of silver ions and/or soluble silver complex made available in the undeveloped and partially developed areas of a silver halide emulsion as a function of development to liberate a more mobile and diffusible color-providing moiety in an imagewise distribution corresponding to the imagewise distribution of said ions and/or said complex. The subsequent formation of a color image is the result of the differential in diffusibility between the parent compound and liberated color-providing moiety whereby the imagewise distribution of the more diffusible color-providing moiety released in the undeveloped and partially developed areas is free to transfer. Color-providing compounds useful in the above processes form the subject matter of U.S. Pat. No. 4,098,783, a continuation-in-part, of said U.S. Pat. No. 3,719,489.
Compounds disclosed in the aforementioned patents as useful in liberating a reagent in the presence of said silver ions and/or silver complex are sulfur-nitrogen compounds containing the group ##STR6## or --S--X--N.dbd. wherein X is ##STR7## These sulfur-nitrogen compounds may be linear or cyclic in structure, and in a particularly preferred embodiment are cyclic compounds, such as thiazolidine compounds which comprise a colored dye radical having a chromophoric system of an azo, anthraquinone, phthalocyanine or other dye and a thiazolidine-2'-yl moiety which may be bonded directly to said dye radical or indirectly through an appropriate linking group. For example, the linking group may be --CH.sub.2 CH.sub.2 O-- as in compound (33) at line 10, column 22, of said U.S. Pat. No. 3,719,489, or it may be CH.sub.2 CH(CH.sub.3)N&lt; as in compound (34) in column 35 of said U.S. Pat. No. 4,098,783.
Copending commonly assigned U.S. application Ser. No. 500,414, filed June 2, 1983 now U.S. Pat. No. 4,468,450 discloses photographic processes and products for forming an image in dye from a colorless precursor of a preformed image dye which is substituted with a moiety containing a thiazolidinyl group, said thiazolidinyl group (a) being capable of undergoing cleavage imagewise in the presence of an imagewise distribution of silver ion and/or soluble silver complex and (b) possessing a substituent on the carbon atom in the 2-position which, upon cleavage of the thiazolidinyl group, undergoes a .beta.-elimination reaction followed by an intramolecularly assisted displacement reaction, which moiety maintains the precursor in its colorless form at least until said thiazolidinyl group undergoes cleavage.
For a definition of a .beta.-elimination reaction see J. March, Advanced Organic Chemistry, Reactions, Mechanisms and Structure, 2nd Ed., 1977, McGraw Hill, N.Y., pp. 895-922, particularly pp. 904-908. For a discussion of anchimeric assistance see J. March, op cit pp. 280, 310 and 311.
The present invention relates to photographic products and processes which exploit another sequence of reactions to form image dyes from a color shifted dye precursor of a preformed image dye. According to the present invention the acyl group which color shifts or decolorizes the dye chromophore is independent of the assisting group thereby being capable of providing surprisingly faster generation of the image dye in the photographic process.